An electronic apparatus such as a personal computer is equipped with various electronic devices, inside its housing, such as a CPU (Central Processing Unit), a memory and an IO (input/output) controller. Such electronic devices are composed of various electronic components including active elements such as a transistor and passive elements such as a capacitor. These electronic components generate heat when the electronic apparatus is in operation. Because the heat could exert an adverse effect on the performance of the electronic components, it needs to be discharged to an outside of the housing of the electronic apparatus. For the discharge, it is generally conducted to take the outside air into the housing by a cooling fan and thus exhaust the inside air, and thereby discharge the heat.
In an electronic apparatus such as described above, which performs cooling of the inside of its housing by a cooling fan, the temperatures of the electronic devices are monitored, and in accordance with measured temperature values, the rotational frequency of the cooling fan is controlled. That is, a control unit or the like for controlling the rotational frequency of the cooling fan performs control in a manner to increase the rotational frequency of the cooling fan when the temperatures of the electronic devices have risen, and in a manner to decrease the rotational frequency of the cooling fan when the temperatures of the electronic devices have dropped.
For example, Japanese Patent Application Laid-Open No. 2007-226617 discloses a cooling system which prevents excessive cooling operation of a cooling fan in an electronic apparatus. This electronic apparatus controls operation of the cooling fan based on reference set values, which are set in a thermal action table (TAT), when electronic devices inside it are in operation in a load state. Specifically, when the temperature inside of the housing has risen and a temperature value detected by any one of temperature sensors has reached a corresponding one of the reference set values, the electronic apparatus performs control to cause the cooling fan to operate to increase its rotational frequency in accordance with the reference set value. On the other hand, when the temperature inside of the housing has dropped, the electronic apparatus performs control to cause the cooling fan to operate to decrease its rotational frequency in accordance with the reference set value.
Japanese Patent Application Laid-Open No. 2011-209146 discloses an electronic apparatus which can determine presence or absence of a failure of a temperature sensor among a plurality of temperature sensors.
Further, International Patent Publication No. WO/2010/041500 discloses a backlight unit which identifies whether a temperature sensor is in normal or abnormal operation from measured temperature data, and controls the brightness of an LED (Light Emitting Diode) whose temperature is being measured by an abnormal temperature sensor, based on substitutive temperature data, instead of measured temperature data by the abnormal temperature sensor.
In such electronic apparatuses as described above which, by a cooling fan, cool down the temperature inside their housing which is raised by the electronic components' heat generation, there are provided temperature sensors for measuring respective electronic devices, and the rotational frequency of the cooling fan is controlled in accordance with temperatures measured by the temperature sensors. Accordingly, in such electronic apparatuses, if any one of the temperature sensors is in failure, it becomes impossible to appropriately control the rotational frequency of the cooling fan. In such a case, for placing priority to the cooling, it is usually conducted to drive the cooling fan at its maximum rotational frequency.
However, if the cooling fan is driven at its maximum rotational frequency when any one of the temperature sensors is in failure, as mentioned above, it leads to excessive operation of the cooling fan, and thus raises a problem in that unnecessary power consumption is increased and also in that noise is increased.
As a method for solving this problem, duplexing of each of the temperature sensors can be considered. In such a case, because even when one of a duplexed pair of temperature sensors is in failure, a value measured by the other temperature sensor can be acquired, the rotational frequency of the cooling fan can be controlled appropriately. However, the duplexing of temperature sensors causes increase in cost.
Patent Documents 1 and 2 disclose nothing about a measure to deal with failure of a temperature sensor. In the technology disclosed in Patent Document 3, when a failure is detected in a temperature sensor, a value measured by a temperature sensor neighboring the abnormal temperature sensor is employed as substitutive data. However, because the neighboring temperature sensor measures the temperature of a different heat source, it cannot be said to be an appropriate substitute for the temperature sensor having detected the failure.